Salem 1 is one of three reactors at PSEG Nuclear‚??s complex along the Delaware River in Salem, N.J. / Gary Emeigh, The (Wilmington, Del.) News Journal

by Jeff Montgomery, The (Wilmington, Del.) News Journal

by Jeff Montgomery, The (Wilmington, Del.) News Journal

WILMINGTON, Del. -- Federal regulators have ordered dozens of Central and Eastern U.S. nuclear plants to conduct new earthquake hardiness assessments based on recently increased risk ratings, including reactors along the Delaware River.

All 60 nuclear sites must submit plans by Dec. 31 for studies to prove they can shut down safely and maintain cooling for reactor cores and spent fuel in the event of a damaging shake. Owners have to account for specific soil and rock conditions at their sites, and make immediate upgrades if needed.

No region in America has so many people living within the overlapping 50-mile planning areas of so many nuclear power reactors as northern Delaware and nearby areas in Pennsylvania, New Jersey and Maryland, according to a review of nuclear sites and U.S. Census Bureau statistics by The News Journal.

One nearby operation ‚?? Exelon Corp.'s Peach Bottom plant along the Susquehanna River in Pennsylvania less than 30 miles northwest of Newark, Del. ‚?? was ranked among the three highest risk priorities for the Nuclear Regulatory Commission's Northeast region, with a December 2016 deadline for completing any needed upgrades. That ranking emerged after engineers found that the earth under and around Peach Bottom could move and shift more violently than assumed in past "safe shutdown" scenarios.

All of northern Delaware as far south as Smyrna lies within 50 miles of Peach Bottom, one of the distance limits used for NRC radiation emergency planning. A report by NRC researchers filed late last year and based heavily on Peach Bottom conditions said that a "significant" radiation plume could reach to and beyond that 50-mile radius if a quake severely damaged the site's spent fuel storage pool.

Behind the orders are concerns that arose after Japan's Fukushima earthquake and tidal wave reactor disasters in 2011 and the NRC's release of a report the same year that showed higher-than-assumed risks of earthquakes strong enough to damage reactor cores at many plants in Central and Eastern areas.

Risk-rate increases ranged from 90 percent at PSEG Nuclear's Salem reactors to 155 percent at PSEG's Hope Creek plant and 189 percent at Peach Bottom. Salem and Hope Creek both are in southern New Jersey.

At some plants in the Central United States, revised risk calculations rose by as much as 24-fold.

"The NRC continues to have confidence that plants can operate safely while more analyses are performed," said Neil Sheehan, spokesman for the NRC's regional office near Philadelphia. "This is based on our understanding of both reactor design and constructions, as well as the results of the visual inspections done at the plants.

The NRC gave 60 reactor sites rankings from 1 to 3, based on company evaluations of safe shutdown likelihood under updated ground movement and earthquake risk calculations. Peach Bottom in Pennsylvania, Indian Point in New York and Pilgrim in Massachusetts received highest priority "1" rankings in the Northeast. Oyster Creek near the Atlantic Coast in southern New Jersey ‚?? the nation's oldest operating commercial reactor ‚?? received a 2.

Exelon's two Limerick reactors northwest of Philadelphia and Salem Units 1 and 2 received a "conditional" rating of 3, with a determination to be made about future requirements and rankings after they submit a report in December. Third-ranked plants have a Dec. 31, 2020, deadline for detailed evaluations and upgrades if needed, while second-ranked have until Dec. 31, 2019.

Hope Creek was unranked and found to meet safety targets, along with 11 other sites.

"This was expected," said Joe Delmar, spokesman for PSEG Nuclear. "As with all the Fukushima related regulations, we will review the new rules and if needed take appropriate action to ensure the continued safe operation of Salem and Hope Creek."

Calvert Cliffs, along the Chesapeake Bay long Maryland's western shore, rated a 3.

Norm Cohen, who directs the anti-nuclear power group Unplug Salem, said that the NRC needs to do more, faster, to assess and respond to findings about heightened risks from both earthquakes and hurricane-driven tidal surges and flooding at Salem/Hope Creek.

"At least it's positive," Cohen said of the clear NRC actions, adding that local critics have long been concerned about earthquake damage risks because of Salem/Hope Creek's location on Artificial Island, built up along the river with dredge spoils.

A report developed for the NRC in 2011 raised the calculated risk of a core-damaging earthquake for Salem/Hope Creek by 90 percent compared with calculations in 1989, putting the annual chances of core damage at 1-in-90,909. The new Hope Creek plant's risk rating rose 155 percent, to a still relatively low 1-in-357,143 ratio.

Limerick had the third-highest risk nationwide, one chance in 18,868 per year. But Exelon's detailed assessment, delivered in March, found that safe shutdown requirements met NRC targets for the reactor, while spent fuel storage areas also remained safe.

Peach Bottom was rated at a 1-in-41,667 chance.

"It's important to note that nuclear power plant designs already include a significant margin of safety with respect to the effects of large earthquakes" the NRC's Sheehan said. "This margin means the plants can survive stronger ground motion than that used in its seismic design."

Federal officials have looked in greater depth at the hazard in recent years, including a report that used Peach Bottom as a meltdown case study, released in 2012. That report concluded that a prolonged loss of outside power at Peach Bottom, as happened at Fukushima, could trigger a meltdown and radiation release. But evacuations would hold down casualties, and much of the radiation would remain inside the reactor, with releases occurring more slowly than in past estimates that predicted high numbers of fatalities.